Put a split back the way it was, while that is still possible.
Where this is in the app
Dashboard → open the return → Assets tab → open the original asset → Split Lineage card → Undo split
The pieces collapse into the original asset and its figures are restored exactly. This works because the original was reduced rather than replaced.
Where the button is
Open the original asset, not one of the pieces. Its page carries a Split Lineage card listing Split into N assets, and below that an Undo split button.
Click it and the card asks "Undo this split? The pieces collapse back into this asset." Confirm with Confirm undo. Pieces have no undo button of their own.
What undo does
Every piece's figures are added back onto the original, penny-exact.
The piece records are removed.
The original's description is restored to what it was before the split, including if you renamed it during the split.
A Split Undone entry is added to the asset's history, reading "Split undone — pieces collapsed back into this asset."
When undo is refused
The button is disabled and an amber panel lists the reasons. Undo works only while the split is exactly as you made it.
A piece is missing or was deleted. The original state can no longer be reconstructed.
A piece has been edited since the split. Any change to a piece after the split blocks the undo. The message names the piece.
A piece has been disposed. The message names the piece. See the warning below.
There is no split to undo. Either the asset was never split, or its most recent split has already been reversed.
Only the most recent split that has not been reversed is undoable.
Disposing a piece ends the undo permanently
When a piece has been disposed, the block message reads:
Undo is blocked: a piece from this split has been disposed. Reverse the disposal first, or this split cannot be undone.
Following that instruction does not restore the undo. Reversing the disposal clears the disposal reason, but recording it counted as a change to the piece, so the "edited since the split" reason takes its place and Undo split stays disabled. There is no sequence of steps that reopens it.
Once you have disposed of a piece, treat the split as permanent. The two records stay separate, and putting them back together means editing them by hand.
The practical rule
If a split came out wrong, undo it before you touch the pieces. Editing or disposing a piece is the point at which undo stops being available and fixing it by hand becomes the only route.